The invention relates to a low-voltage circuit breaker with a retrofittable motor reset mechanism, whose output shaft can be coupled to a charging shaft, mounted in a bearing block, of the spring energy store of the low-voltage circuit breaker.
Low-voltage circuit breakers generally have a manual drive as basic equipment, in which a spring energy store is charged with a specific predetermined number of movement strokes. The xe2x80x9cchargedxe2x80x9d state of the spring energy store is then indicated, and the breaker is ready to be switched on if the other interlocking conditions, such as xe2x80x9cdoor closedxe2x80x9d, xe2x80x9ccrank of the traction drive withdrawnxe2x80x9d, and the like are met.
For higher demands on management or convenience, there is then additionally the motor reset mechanism. Because the manual reset mechanism is the basic embodiment and the motor reset mechanism is an additional piece of equipment, the motor reset mechanism is designed in such a way that it forms a retrofittable unit. In this case, it is intended for retrofitting to be possible even in switches which have already been installed in a switching system. This is to be possible without a great deal of effort.
The motor reset mechanism unit generally includes of a housing in which there is a geared motor, whose gearbox has a large reduction ratio and whose output shaft is coupled to the charging shaft of the spring energy store of the low-voltage circuit breaker, on which shaft the manual reset mechanism also acts.
U.S. Pat. No. 4,901,821 shows, in particular in FIG. 3, the fixing of a motor gearbox unit for the reset mechanism of the spring energy store of a low-voltage circuit breaker, in which this motor gearbox unit is fixed to a supporting plate by means of screws. This necessitates access to the screws from one side of the supporting plate, and space to attach the motor gearbox unit from the other side of the same. Subsequent installation of the motor gearbox unit in a low-voltage circuit breaker incorporated in a switching system is not possible in this embodiment.
In addition, a motor gearbox unit, described in U.S. Pat. No. 4,649,244, for resetting an energy store in order to switch off a low-voltage circuit breaker is not suitable for subsequent incorporation from the front in a switch located in a switching system. All the previous embodiments of motor reset mechanisms for charging spring energy stores in low-voltage circuit breakers permits installation only from the side of the low-voltage circuit breaker, that is to say not in switches incorporated in a switching system. The trouble-free retrofitting of such switches in a switching system is therefore not possible.
Consequently, the object of the present invention is to provide a fixing means for motor reset mechanisms which permits the same to be installed from the front side of the low-voltage circuit breaker, and therefore permits the retrofitting of such switches in a built-in position.
In order to achieve this object, according to the invention, centering elements are provided on a flange of the bearing block of the charging shaft of the spring energy store so as to engage in mating elements on the gearbox output of the motor reset mechanism, into which centering elements of the motor reset mechanism can be pushed axially with little travel in the direction of the charging shaft. The small axial travel or movement needed when the motor reset mechanism is pushed into the centering elements permits the subsequent installation of the motor reset mechanism from the front side in a switch incorporated in a switching system, if retrofitting is desired. The motor reset mechanism can be pivoted in these centering elements and is pushed into these centering elements in a position in the switch in which it is pivoted in the direction of the front side of the switch. At the same time, the coupling between the gearbox output and the charging shaft of the spring reset mechanism is also produced. Furthermore, in order to lock the motor reset mechanism in the pivoting direction, a fixing means is provided at a point fitted at a specific distance from the centering elements. In addition, there are means for fixing the motor reset mechanism axially in the centering elements of the flange of the bearing block of the charging shaft of the spring reset mechanism, and in the coupling of the charging shaft.
Consequently, some features of the conventional motor reset mechanism are maintained, in particular the face toothing on the shafts to be coupled to each other, and the sprung pressing device for the stub axle of the motor reset mechanism. The fixing means for locking the motor reset mechanism in the pivoting direction can advantageously comprise a latching element on the motor/gearbox block of the motor reset mechanism, and a spring latch means arranged in the insulating parts on the breaker frame. However, it can also be formed by an eye on the motor/gearbox block of the motor reset mechanism, a threaded hole in a stop and a screw which can be screwed into the threaded hole through the eye. The significant factor in every case is manipulation in the installation direction of the motor reset mechanism, that is to say from the front side of the low-voltage circuit breaker.
The means for fixing the motor reset mechanism axially in the centering elements of the flange of the bearing block of the charging shaft of the spring reset mechanism, and in the coupling of the charging shaft, is advantageously a rigid supporting arm which is fitted to the bearing block of the charging shaft of the spring reset mechanism and has an integrally molded angle.
In an alternative embodiment, the means for fixing the motor reset mechanism axially in the centering elements of the flange of the bearing block of the charging shaft of the spring reset mechanism, and in the coupling of the charging shaft, can also be a springy wire loop which is fixed by hooks in holes in the bearing block of the charging shaft of the spring energy store and which encloses the motor reset mechanism and can be locked in latching elements provided for the purpose on the motor reset mechanism. Before the motor reset mechanism is incorporated, this wire loop is mounted by means of the holes. The hook-like ends of the wire loop and the holes are dimensioned such that the wire loop can hang downward and does not impede the insertion of the motor reset mechanism. It is additionally dimensioned such that it encloses the motor reset mechanism. The final position of the motor reset mechanism is defined by suitable stops and, in this end position, the wire loop can be pulled up from below over the motor reset mechanism and locked in latching elements provided for the purpose.
A wire loop of this type for fixing a structural element, here an extinguishing chamber for an item of electrical switchgear, by means of a springy wire clip, is described in DE-A 1 908 751 for example. An identical fixing means for fixing distributor caps in ignition distributors of motor vehicles is generally known. However, in all the known cases, they are used only for fixing passive elements, which are not subjected to any significant mechanical stresses. The advantage of the wire loop in the present application resides in the fact that it does not in principle have to be incorporated, like the rigid supporting arm, regardless of whether it is needed at all or not. It is also cheaper and can be supplied together with the motor reset mechanism. Of course, a combination of the two fixing means can also be used.